1. Field of the Invention
The present invention relates to a secondary battery including a current interruption mechanism.
2. Description of Related Art
Conventionally, a technique in such a field is described in Japanese Patent Application Publication No. 2014-137891 (JP 2014-137891 A). In a secondary battery described in this publication, a current interruption mechanism is configured such that a positive current-collector projection formed in a cylindrical shape in an upper end of a positive collector terminal inside the battery is joined to a top portion of an inverting terminal having a bowl shape and connected to a fastening member (a terminal) that enables external connections. Furthermore, a top plate portion is placed in a top portion of the positive current-collector projection via a vulnerable portion, and the top plate portion has a passage hole that reduces a pressure difference between an inner side of the battery and a gap between the inverting terminal and the top plate portion.
In such a current interruption mechanism, when the battery becomes a high temperature at the time of use, a gas pressure inside the battery increases and gas inside the battery pushes up the inverting terminal through the passage hole, so that the inverting terminal warps upward. This breaks the vulnerable portion, so that the top plate portion joined to the inverting terminal is separated from the positive current-collector projection. As a result, the positive collector terminal placed inside the battery is electrically disconnected from the fastening member (terminal) for external connections, so that current supply to the fastening member is stopped and the battery is brought into an unusable state.